It has recently become known that an organic-inorganic composite material prepared by dispersing a clay composite having an interlayer distance of several nanometers, e.g., by ion exchange with an organic salt, into a polymer resin and processing the mixture, exhibits high mechanical strength and heat resistance suitable for use in the manufacture of automotive, aircraft and building components.
However, the addition of a clay composite to a polymer does not always give the above-mentioned effect, and such composite product with improved characteristics can be obtained only in very limited cases, e.g., in 1) a case that a layered clay composite is added to a monomer and/or oligomer of a resin during a polymerization step (see U.S. Pat. No. 4,889,885; and [A. Usuki et al., J. Mater. Res., vol. 8 (1993), p1179]), and 2) a case that a layered clay composite is added to a copolymer of polypropylene and anhydrous maleic acid during an extruding step (see [M. Kato et al., J. Appl. Polym. Sci., vol. 66 (1997), p1781]).
However, the method of case 1) has the disadvantage that it is very difficult to uniformly disperse the clay composite into the polymer matrix, resulting in poor product quality. As to the method of case 2), the use of an expensive polymer, i.e., the copolymer of polypropylene and anhydrous maleic acid, causes the problem of a high manufacture cost.
Hitherto, there has not been reported a satisfactory method of preparing a high quality nano-sized organic-inorganic composite material at a low cost.